Conventionally, as a method of bringing reactants in a fluid form in contact with each other, and mixing the reactants with each other, thereby producing a reaction product, a method of using a multichannel apparatus so-called microchannel reactor is known.
The microchannel reactor includes a substrate on a surface of which minute groves are formed, and the minute grooves formed on the surface of the substrate construct reaction channels for mixing the raw material fluids with each other. The multichannel apparatus causes the raw material fluids subject to the reaction to flow in the reaction channels, thereby drastically increasing a contact area between the raw material fluids per unit volume, resulting in an increase in efficiency of the mixture of the raw material fluids. The microchannel reactor is used for applications such as production of chemical products and medicines.
Patent document 1 discloses a microchannel reactor as an example of the multichannel apparatus. The microchannel reactor includes first introduction channels through which a first reactant (first raw material fluid) required for a reaction in the reactor flows, and second introduction channels connected to a middle portion in a flow direction of the first introduction channels through which a second reactant (second raw material fluid) flows. The first reactant which has flown through the first introduction channels and the second reactant which has flown through the second introduction channels cause a chemical reaction at confluence portions of both of the introduction channels, and a generated reaction product is brought via the first introduction channels to an outside of the reaction channels.
On the other hand, the multichannel apparatus having a structure such as the microchannel reactor is sometimes used as a heat exchanger for heating a subject fluid.
If the microchannel reactor disclosed in Patent Document 1 is used to bring the raw material fluids into contact with each other, and to mix the raw material fluids with each other, the following problem occurs.
A case where a first raw material fluid A and a second raw material fluid B are introduced into a microchannel reactor, and are caused to react with each other in the reactor as shown in FIG. 2 is considered, for example. On this occasion, it is assumed that the first raw material fluid A and the second raw material fluid B respectively of 100 in volume flow rate are supplied, and a reaction product C of 200 in volume flow rate is generated as a result of the reaction between both the fluids. In this case, a residence period of 10 seconds is necessary for the production of the reaction product and the discharge of the reaction product out from the reactor after the raw materials are supplied into the microchannel reactor.
By the way, the reaction is possibly carried out by using the fluids in smaller amounts. The first raw material fluid A (volume flow rate of 50) and the second raw material fluid B (volume flow rate of 50) are introduced into the microchannel reactor, and are caused to react with each other in FIG. 3. In this case, the flow rates of the raw material fluids are small, and the flow rate of the generated reaction product decreases accordingly. However, even if the flow rate of the generated reaction product decreases, capacities of the channels remain the same, a period during which the raw materials and the reaction product flow through the microchannel reactor increases, and the residence period thus increases. For example, while the residence period is 10 seconds in the example in FIG. 2, the residence period increases to 20 seconds in the example in FIG. 3. As the residence period increases, a reaction period increases, and as a result the reaction proceeds excessively or unnecessary reactions occur. Therefore, even if the reaction product of 100 in volume flow rate is produced, a possibility of a component of the reaction product becoming a component C′, which is different in quality from an intended component C, cannot be denied.
In other words, some reaction products to be produced by the microchannel reactor generate unnecessary byproducts or present a decrease in yield of an intended reaction product by an amount corresponding to an increase in amount of byproducts if the period residing in the reactor is too long. Thus, it is preferable to provide certain means for maintaining a constant residence period of the reaction product in the reaction channels regardless of supply amounts of the raw material fluids in order to obtain the reaction product having a stable quality in the microchannel reactor even if supply amounts of the raw material fluids decrease.
Of course, it is conceivable to adjust the flow rate and thereby maintain the residence period of the reaction product by a way of preparing a plurality of reactors and operate a required number of the reactors, or closing some of reaction channels provided for a reactor by any way, etc. However, it is extremely difficult to provide such means due to an economical problem and in terms of such a point that the structure of the multichannel apparatus is minute.